Multi-engine control means



April 3, 1956 A. w. BLANCHARD MULTI-ENGINE CONTROL MEANS 2 Sheets-Sheet l Original Filed May 14, 1949 @NN mmjmn om@ o...

April 3, 1956 A. w. BLANCHARD 2,740,260

MULTI-ENGINE CONTROL MEANS Original Filed May 14, 1949 2 Sheets-Sheet 2 AxlAl. MoTloN oPERArEs 50 STAGGERED THRoT'rLE CONTROL .4 5 I ROTARY MoTloN oPERATEs MASTER TRANSMITTER IN VEN TOR.

ALLEN W. BLANCHARD United States atent Aviation Corporation, Tetcrboro, N. J., a corporationI of Delaware -Original application May 14, 1949, Serial No. 93,215,

now Patent No. 2,667,148, dated January 26, 1954. Divided and this application August 17, 1949, Serial No. 110,819

16 Claims. (Cl. 60-97) The present application is a division of my copending application Serial No. 93,215 filed May 14, 1949 and nou.l U. S. Patent No. 2,667,148 granted January 26, 1954, and

Figure 2 is a diagrammatic View illustrating the novel multi-engine control. l

Figure 3 is a perspective view of a modified form of the control.

In the drawings corresponding parts are indicated by likenumerals and in order that the improvements forming the subject matter of the present application may be better understood, the electric control system shown in Figure lwill be first explained in relation to the parts thereof yheretofore disclosed and claimed in the cepending applicationSerial No. 561,083, filed October 30, 1944 by Joel D. Peterson.

Referring in detail to the electriccontrol system of Figure l, there is provided a single lever and a compound clutch 2, whereby an induction throttle valve of an aircraftengine may be selectively connected either to an v automatic control system or directly to the control lever relates to improvements in control systems and apparatus for the power units of aircraft of the type disclosed and claimed in the copending application Serial No. 561,083 filed October 30, 1944 by Joel D. Peterson.

With present aircraft supercharged engines the best per formance is maintained only by adjustment of the various functions of the engine to values consistent with eticient and safe operation of the engine, with proper compensation for external factors such as the atmospheric pressure surrounding the aircraft, which pressure is directly affected by changes in the altitude ot` the aircraft. The functions of the power unit controlled are engine manifold pressure Another object of the invention is to improve the con-l 1 forl manual operation.

The clutch 2 may be of a type such as shown in detail in the lcopending application Serial No. 561,083 and includes an electromagnet which when energized operatively connectsthe arms 28 and 30, as shown in Figure 1.

The arm 2S is operably connected through a rod 39 to the automatic control mechanism, while the arm 30 is connected through a rod 40 to the throttle control valve. Thus upon, energization of the electromagnet 20, the throttle control valve is operably connected to the control system through the arms 28 and 30.

When the electromagnet is de-energized, a spring biases the clutch so as to disconnect the arm 28 from driving relation with the arm 30 while drivingly connecting the arms 49 and 30.V As previously` explained,

trol system disclosed and claimed in the aforenoted` cothe setting of the control system of one engine relative to t the other.

Another object of the invention is to provide a novel single lever control for multi-engine operation to permit adjustment of the engine power at opposite sides of-the plane to overcome tendency of the plane to veer from its course in take-oil due to engine torque and cross winds.

Another object of the invention is to provide a novel :r

single lever control for the control systems of two or more engines supplying 'balanced power to anaircraft and further provide novel means for selectively varying the power applied at one side or the other of the air- Y craft by such engines.

During take-off, the natural tendency is for a balanced power multi-engine aircraft -to veer or turn from a fixed course due to engine torque or the direction of rotationof the propeller blades. In order to steer the airplane in a xed direction under such conditions, the engine power at one side of the plane may be reduced so as to balarice the tendency of the plane to veer. This expedient may also be used to overcome the tendency of cross winds to change the direction of the craft.

The above and other objects and features of the invention will appear more fully hereinafter from a con* sideration of the following description taken in connection with the accompanying drawings wherein several embodiments of the invention are illustrated by way of example.

Figure 1 is a diagrammatic illustration of the control j system.

the arm 30 is connected through rod 40 to the induction throttle valve as shown in detail in the aforcnoted application Serial No. 561,083.

Thus when the clutch 2 is tie-energized, the automatic electrical control system is inoperative and the induction throttle valve may be manually kadjusted through operation of the pilots control lever 1. A double pole switch 60 is provided to energize or cie-energize the automatic control system simultaneously with the electromagnet 20 through electrical conductors 61, 62, 63 and 64 so that the induction throttle valve may be automatically or manually controlled as desired. Moreover, it will be readily seen that as a safety provision upon a power faili ure the system will be automatically transferred by the de-energization of the electromagnet of the clutch 2 to manual operation.

The pilots throttle control lever 1 is further suitably connected so as to effect selective electrical control of the automatic electrical control system. Thus the lever 1 is connected by an actuator rod 70 to an arm 71, which is operably connected through a shaft 72, a gear train 73, and shaft 74 to rotor 77 of an electrical induction type transmitter or transformer 76.

The transmitter 76 as illustrated hereinafter, comprises the rotor winding 77 which m`ay be angularly displaced in relation to stator windings 78, 79 and 30 by the control lever 1, and the rotor winding 77 is arranged in inductive relation with the stator windings. Voltages are applied to the rotor winding 77 through electrical conductors 77A and 77B connected to conductors 63 and 64 leading from a suitable source of alternating current. Angular displacement of the transmitter rotor winding 77 causes the voltage applied to the rotor winding 77 to induce varying voltages in the stator windings 78, 79 and 80 of the trans- Vtransformer or receiver 93.

Propeller pitch governor control Rotatabiy mounted Within the stator windings-*90, 91 and 92 and in inductive relation therewith, is a rotor Windingf94. if the winding Misnotina-positionin relation to the stator windings 99, 9i and 92 corresponding to1a-- positionfatrightangles to the inducediieldortlie relative position of the rotor Winding '77 to the statorlfwidingsr 7S; 79 Lancl'ib there'will be induced into therotor winding., 94avoltage. Therotor winding 94'is connectelthrougir?-A eleetrical conductors itiand 101 tothe 'inpuboffanamplier- 110. The voltage induced into the-winding`-94 will cause an alterna-tingcurrentvto flow to the'arnpliiier 1101,A which is in phase or in phase#oppositionewitl-thealternating current -ow supplied through;-the-epndnctors-f 63 and 64, depending upon the directionofethe difference inlthepositionofthe rotors77 and 94.4V

The :amplifier 10'-rnay Vbel of^any-suit`ablee type-fof l torque amplifier well known in the` art;k or'may 'be'ampli e'r-'of-:a'1type-such asshown, for examplein theflexpired^ patent No.-l,586,1233, datedAMay 2551l926and1grantitoJ4 H. Anschutz-Kaempfe. Electrical condctorsduand 112-lead:fr'orn theroutput oiathe amplier'illotoasecondaryvor auxiliary Winding `113 of-a -two=phase1motor -1`1 4.1/ Aunain winding 115 l is connected through electrical iconrv ductors 115A andy 115B which are-connected :to-confine-M tors 63 and i4-leading-v to the sarne-y alternating Leur-rent sourcerasf the transmitterv motor Windingflflzl Thus itthe-rotor-windings77 andf-94 are-set-finY-suclraa manner in relationfto the stator windings; that novoltage-\ is induced into the --Winding-94no current -willflw iritheaV auxiliary motor Winding-113 of the-tWo-phasemotor 1143* forf therewould be no alternating current `flowing giriL 'the input circuit 100 and 101V ofthe amplifyingunit1110-. Tl'elk motor 114Will therefore not operate for y-thereisno rotate-1 ingviieldf.. Y

Whenztherotor windings'l and 94lare-positioned-at== dierent angularA relations tothe stator windings-ifrorrrtlreA null position, a voltage will be impressed onl the-windingl 94,-zthatiistosay on the input circuit- 100 fand 101' of-the amplifier 110;. and the said voltage willibe-inphaseoriri'l` phase:l opposition with, :the voltage supplied) througlfri-tl'r'ef conductors 63 amd64. i

Thenampllied` current which ows in thevr auxiliary@ windingllS, will4 thus produce-a corresponding ildi v Provision is, furtherfmadein the amplifier. y11th-in.arr1an'-45 nersfor. lexample such as shown. in the. patent:previt l.lsly11 noted;to Anschutz-Kaempfe, whereby the.saidefauiriloJ iary ,currentor auxiliary lield` will have fa phaseldisplacee. ment or ditercnce--of 90;.degrees relative tor-the mainn current or; main: rheld, so that. saidelds form.togetlnerffa` 50 rotating field of sufficient magnitude to startethegxmotortu 114i; Itwill depend on: the. phasedirection of ther alternatingacurlent Voltage at. thetinputr of therarnplierd'lflJ-I whethenithe. auxiliary ,field Willi-be displaced 90; degrees-a relatiyleftoy thezmain lield in;the1forwardfor backwandrdn 455l rection or in-other, .,words., the directionz or :rotationzofth'e :f rotating field willldepend; upon::the direction of angula'ni variation of the rotor winding andi94n Y Themotor .114 is so arranged thatif. the, receiyer;rotor 94 is not inta positioncorresponding tothe nullxpositiom, 60 for. that. of the transmitter rotor 77 van'electrical signaLis.` appliedtto the amplifier which will feedcpower: to the:` motor 114- to. cause rotation of the 4receivenzrotorr=94e` through a shaft 114A and interconnecting` mechanicali;A means, aswll be explained, sowas Vto*bringethe;receivenr rotor; 94m a position'corresponding to theE-null position t for the position of. the transmitter-rotor 77; whereupon-1. thesignal ofthe input circuit ofv the(,arriplitiert-llywill;v cease-and rotation of theVA motor 114.y terminate.

The-rotor of the motor 114 is connectedifbyrth'e'shaftzim 114AI through a suitable gear train 116 and. shaft-117210: an -Aarrn H8 to :which is.. connectedafrod; 11931saclingrtotyau suitable propeller pitch governor control.

The: rotor winding 94-follows up Vor measures for eactni corresponding change of position--otlfthe*transmitterytlie- @umanoi- 4. Settnsptthenropellettpitch governati Thescyemotis. actuated by the follow-up motor 114, and its ratio of movement is controlled by reduction gear train 116 and a cam 131, to thereby position the follow-up rotor winding 94 of the receiver 93 shownzinx-Figure 1, so as to maintain proper relationship between theengine speedand mani. fold pressuregI as will-'beexplained:v To=provide`for this n ratiofperformance there lis provideda rotor: shafLil-'ijza` ongyvhich: istmounteda follower 133 ,whichmayfbefbiascd under suitable spring means not shown, inta-,contacting relation withthe cam surface of cam 131. The followen. 133. iaarrangdto position the receiver rotor '-windingy94" tlugopghi the motor A 114: and cam, 131"accordinggto, the movement of the pilots control lever 1, until thepsitifon of the rotor 94 agrees with that of the transmitter rotor 77.

The earn 131 provides a non-lineal continuous smooth cur-yaoi actuation;, for 4- thegovernori': not shown, z. and Whih zcofaets 1 with.:rhe :selected: position;l ofrthei transe, mit m7611051 maintain tproperrspeedx. relationships@ of .theo enginsitcthcse-seleetedby the-pilotv t u Thun-asin the-other ,followup .motori anangermn1tn1 oggthe; `several actuators hereinafter; tof bef; described; the` rotor two-phase motor;114'iin;-the;governor 'actuatorf;s energipelty and ,.angularlypositioned laecordinglygm a E selectedaposition? othev master *.transmitter:y 76 i to thereby; actuatdefrod .119; throughleven11,8;` mountedon cam shait '1 117 nntilv, rotor94oflthe governor,y followrupftransmrmer;,- 93? y.arrlttulil:r-l'ytshifted'teP1--I1Ul1..ps stion fQr-.-nof.v0lt ase. output-to amplitier; 100..

Therodv 119,\is Aco,lllltectedfto a propeller, pitch ,-governorf.y control. whichi mayV be :ofany suitabletype welll knowing l therartiorimayfbe eta` type shown-in the.con@ndincaprini:A

cationgrS'eriaLNo. $61,083.l

Y i -f Throttle actlnfztorfv Inxaddition to -operatingethe f propeller lpitch`-governor controlthepositioning ofy 'the A rotor l7'7 alsocontrols vthe positionof#"theiinductionfr'throttle valve which regulates thendctiowpressureof=the engine-aswill be explained: As 'shown Figuref 1,' there is provided a second -re ceiverwliich has -arotor windingj201 andrstatoriwind ing1202,-203 and1-204. The stator t Winding `202"-is connectedftlirough electrical conductors l 87A- andv 287' to thel stato'n windingzioftheetransmitter-765 while--thestator`l-v to. theiinduct-ive'fwinding 205'fso'l that when a rotor winding v 208mth'e induction=switchf206 isi positioned at-ri'ght-'anglcs toethen'windng'a'g'I as shownin' Figure 1,- the-winding 208S3 willibeiinduetive1yjcoupled withlthewinding1205landthere` Wilhbtno incluctivetcoupling between thewindingfZBand-e windin'gZllZt Howeven: whenI the-rotor-winding208i isipositioned at right angles to the windingvztifthetwirrdingJ -motor 220, as will be explained.

As shown in Figure 1, the stator windings 79 and 80 of the transmitter 76 together with the electrical conductors 86, 87, 86A, 87A, stator winding 205 of induction switch 206 and stator windings 202 and 203 of the receiver 200 provide a closed circuit.

There is induced in this closed circuit through the alternating current flowing in the rotor winding 77 a first voltage and through the alternating current flowing in the winding 201 a second voltage which tends to oppose the rst voltage. If the rotor winding 77 be positioned at a different angular relation to the stator windings 7S and 80 and the rotor winding 202. is positioned in relation to the stator windings 202 and 203, it will be readily seen that a greater or less voltage will be induced in the closed circuit by the one than by the other. The difference between these induced voltages will effect a current ow through the high impedance windings 205.

Thus in the event the rotor inductive winding 208 of the switch 206 is positioned in inductive relation to the stator winding 205 a corresponding voltage will be induced in the winding S, which upon amplification by the amplifier 215 will cause an alternating current ow in the auxiliary winding 221 of the two-phase motor 220; such current ilow will have a phase displacement or difference of ninety degrees relative to the main winding 222, so as to effect rotation of the motor 220. The direction of rotation of the rotating iield will depend upon whether the voltage induced into the closed circuit by one or the other of the rotor windings 77 or 201 be greater; the motor 220 being so arranged as to move the rotor winding 201 in a direction relative to the stator windings 202 and 203 so as to cause the voltages induced into the said circuit to equalize, whereupon no current will flow in the winding 205 and rotation of the motor 220 will terminate. The motor 220 drives the rotor winding 201 through a suitable driving means including shaft and reduction gearing 240. The motor 220 also drives through shaft 242, gear train 244, shaft 2-'58 and arm 245, the rod 39 and arm 2S of the electroniagnetically operated clutch 2. The motor 220 upon energization of electromagnet of clutch 2 controls the position of the induction throttle valve. The motor 220 also drives through shaft 248, a cam 250.

An arm 251 rides in contacting relation along the cam surface of the cam 250 under suitable biasing means, such as a spring tension means, not shown. The arm 251 is drivingly connected through a shaft 253, suitable gear train 254, and shaft 255 to the rotor 20S of the induction switch 206 so that upon rotation of cam 250 to a position where the arm 251 rides on raised portions of the cam 250, the rotor 208 will be shifted to a position at right angles to the winding 205 and in inductive relation to winding 207.

It will be readily seen, that with the rotor 208 of the induction switch 206 positioned in relation to the inductive winding 205, the motor 220 effects a follow-up of the position of the transmitter rotor 77. Thus movement of the rotor 77, in a counter-clockwise direction, will effect a corresponding follow-up clockwise movement of the winding 201 and counter-clockwise movement of the cam 250 until a shifting of the induction switch rotor winding 208 in response to movement of the control lever 1 is effected so as to place the winding 208 in non-inductive relation with the winding 205 and in inductive relation with the lwinding 207. Such counter-clockwise movement of the cam 250 will of course effect a corresponding counterclockwise movement of the arm 245 affixed to the shaft 248 so as to progressively open the throttle valve through rod 39, arm 2S, clutch 2, arm 30 and rod 40.

The cam 250 is so arranged that the direct motion follow-up of the rotor 77 is effected for a predetermined range of movement of the throttle valve, such as, for example from full closed position to thirty per cent open throttle position. At the latter predetermined position, the cam 250 will begin shifting the induction switch `rotor winding 208 to a position out of inductive relation with winding 205 and into inductive relation with winding 207. The action may take place for a predetermined range of movement of the throttle valve, for example from thirty per cent to thirty-live per cent open position of the throttle valve.

Manifold pressure control Upon the rotor winding 208 being shifted to a position in inductive relation with the winding 207 the control of the throttle shifts from a position follow-up to a manifold pressure follow-up.

The manifold pressure control includes a receiver transformer 259 having the stator windings 260, 261 and 262 which are connected in parallel with the transmitter stator windings 78, 79 and 80 and the receiver transformer 93, stator windings 90, 91 and 92 through electrical conductors B, 86B and 87B connected respectively to the conductors 85, 86 and 87.

The manifold pressure follow-up arrangement for maintaining the engine manifold pressure in accordance with the pilots selected pressure comprises a two-celled evacuated bellows 265, a take-off rod 266, and a bellows seal 267 for sealing the shaft opening in the casing 268. The rod 266 is connected by arm 270 and shaft 269 to the single phase rotor 271 of the receiver transformer 259. The casing 268 is sealed and connects to the intake manifold of engine 4 by conduit 280.

Thus when the evacuated diaphragm 26S collapses, as the pressure at the intake manifold increases a resulting pull is exerted on rod 266, thereby moving rotor winding 271. Now, if the pressure selected by control lever 1 connected to transmitter '76 is different from the then existing engine manifold pressure, there is a voltage induced in the rotor 271 due to its angular relationship to the resultant field produced in the stator windings 260, 261 and 262. Accordingly, if the position of the rotor 271 which is determined by the engine manifold pressure in relation to the stator windings 260, 261 and 262 corresponds to the null position, there will be no voltage induced in the rotor 271. However, if the rotor winding 271 is not at a null position relative to the position of the rotor winding 77 a voltage will be induced in the rotor 271, the phase of which is determined by the direction of the difference in the relative positions of the rotor winding 77 and 271. The voltage so induced in the rotor 271 is applied through conductor 282 and 233 to the stator winding 207, this induces a corresponding voltage in the rotor winding 208 of the inductive switch 206 causing a flow of alternating current through conductors 210 and 211 to the input of the amplifier 215.

As previously explained, output conductors 216 and 217 lead from the amplifier 215 to the secondary winding 221 of motor 220. The main winding of the motor 220 is connected to the constant source of alternating current by conductors 224 and 225, the phasing between these voltages is such that the motor angularly positions the throttle in such a direction that the resulting increase or decrease in the manifold pressure turns the rotor winding 271 toward the null position to agree with the pressure change.

Thus it will be seen that the throttle is adjusted by the motor 220 so as to maintain a pressure in the intake manifold as selected through manual operation of the control lever 1. Moreover such selected pressure is increased by movement of the control lever 1 in a clockwise direction and transmitter rotor 77 in a counter` clockwise direction requiring a corresponding counterclockwise movement of the rotor 271 to balance the transmitter rotor 77.

After the throttle has been initially opened to a position in excess of a predetermined degree of say sixty per cent, then a further call for an increase in the intake manifold pressure through operation of rotor winding 271 will cause operation of a supercharger as will be explained.

Operation ofithesupercharger will.A cause the;intake manifold pressure torbeincreasedland-asa result thepressure rnernberr265 will"againY apply-voltage tothe throttle actuator motor 22) to return the throttler valve to the sixty per cent reference position. Sztpercharger control inthe;Y event ythe VYthrottle valve. hasqbeen opened to, the predetermined degree of sixty per; centfupon afurf.

ther call for increase in the intake fmallfld Pressure thefurtheropening of the throttle valve will etlect operation of anf auxiliary supercharger.

Theauxiliary supereharger may bedriyen, by suitabl e. driving means such as. a turbine driven-by theexhaus t ses; sfromfthe; engine., and. applied. through. .an exhaust.:

conduit. The auxiliary supercharger; has- A an Aair inlet conduit which may beconnected to.. anv air scoop in a Conventionatxnanner.;

There 4is furth er .provided an air conduit leading from as an auxiliary variable speed motor. means of any suitable type. In the instantcasetheiwaste gate is -controlled byjammotor 31lthrougha rodll.' Themotor 310H beingconnected to the rodll .by a shaft 312; train of; gea-rsld, and shaft 31S connected toan arrn` 320 to 30 which the rod 311 is operably connect ed. Motor 3 10 isofa reversible two-phase type, such as previously def..

scribedhavinga secondary winding 321 Aanda primaryv vri-11611113322. Operation 0f, .the motor-310 is.@naturelleft bywthek transformer 2&0 having rotor winding 201; and stator windings 292, 4293 and 204, as previously enp l ained. v

Afconductoratl leads from the stator winding 2t 2 through conductor SEA to a stator winding lalloit trans; former-335; The transformer SSS-'hasstator windings 331,1 337v'and 33S, the stator winding -331 is conneetedtov thestator winding337 and by electrical conductor-340 through an acceleration over-speedresponsive device,A as l disclosed in the copendingzapplieation Serial No. 56l,083

to theinput of an ampliiierSSll ofsimilar type'to ampli y tiers 110 and 215.

Conductor 35i-leads-from the statorwinding204 of thetransformer20l to the input-offA the amplier'.

Arotor winding 33,6.of the transformer 33Sis connected by conductors 369 andfl to. the conductors 63 and` 64 r.leading fromthe main sourceof alternatingcurrent The frotorll .is soarrangeduinY relation to the stator windings 22 .and 2tl4.ot the -transformer200that upon the. throttlebeingpositioned by the motor 220 to a position less than: a. predetermined null position of, for example-,sixty per cent open, a combined voltage will beinduced-into the windings Ztl?. and 204 which will loeopposed tothe combined voltage induced into the. windings 331 and337 by the alternating current in the transformer 335. The dilerence between suchcombined voltages .will cause; aflow of current to the input of the ampliier, 350: and` through Output conductors 362 and 3531) -thesecondary Avvinding, 32 1.v The said current in thegwindingn having such' a phase relationship with the alternating current owing in the mainwinding 322 as to tend to rotate the motor 310. in. a direction opening point'pfthejhrottle yalve ofsay sixty percent open -has beenlpassed.:

duced`in the windings 331' and 337 and that induced in the windings 202 and 204 by the alternating current Any other suitable driving means for the supercharger may be provided instead of theturbine such (itl in the windingf- 201 willjhavean opposite differenee. Such npredominating yoltagefwill; 'cause a- ,owb currentf l tothe input-ofthe amplifier and tofthe secondary wind# ing 321v opposite to that Y'previously described-1and@theu current flowing in the secondary winding321gwill=bevofiA a phase sueient to-initiate operation of -the -motor' 310 n-'a'idirection Vforclosing the vwaste gate. Y

There -isalso aixed to the shaft -320-a cam 380 on the vcam surface off'which ridesa-cam follower `arm 381 which -adjusts throughL a=shaft- 382,1the-ro-tor winding 336- of the transformer 335:1 A- feature ofthe present-invention over thatidisclosedjby the'Petersonapplication-Serial N o.v 561,08-3f-isthatin the presen-t invention, the-throttle@ valve'followup'transformer200,1the Waste gate follow-up-.l transformer' 335 and lthe ca m13f80 i areso-fdesig1-ied1and'lh adjusted thatY the waste gate will remain opex r=ft )r-avsubstantial part of the throttlerotation from theAclosedY position to, for example, a sixty per cent open position, the waste gate will thenbe'closedby the motor-310 inproportiontothe throttle valvepositionas the throttleA valve is further opened'until zit-aV full open throttlef valve' position 4the wastev gate-willalso be adjusted-to a-- fully -closed position;

It.` will; begseenfrom-the foregoing-that the A. Cpvoltagefrom thethrpttlevalve follow-up transformer-200- is thesignalewhichrcontrolsgthe-waste gate position. The -1 transformer-'ZU-inwthe latter arrangement is so set-that when the throttle valve is fully closed the difference vbetween the combined voltages` induced by transformers '200eand335 isof--such a phase that, when ampliiedandl appliedto'thee waste gate actuator motor 310; it= willi: cause the motor to-fullyV openthe waste gate. As--they throttle valveis opened this voltage falls to a minimurrh ata predetermined vintermediate position--of, for exam-- ple, siXtyper cent'open throttle valve position, and then increases again substantially atdegrees out of -phase- -1 as the' throttle valve is opened past this intermediate position; This` voltage when amplified and appliedto. the waste gate actuatorl motor S10-is then of sucha phase as togcausethegmotor-Sl to close the waste gate. Vo'ltage from the resulting adjustment of the waste 'gatefol-v low-up transformer 33S'thencounterbalances the voltage from the throttle valvefollow-up transformer 200.150

that the positionof-'the waste gate in a closing directionfollows theposition ofthe throttle valve inV an opening-4 direction pasttheintermediate position. The roten-3364 of the wasteV gate follow-up transformer 335^isdrivenfby1 the cam 3$0secured 'to the actuator output shaft 320,'

anda camA follower 381; "secured ,toV the shaft'382 of* the f rotor 33 6.,

The cam 3304s so shaped that upon adjustment-ofgthewaste/ gate Nin a closingdirection in response to tj-signalv voltageL resulting uponv -a further closing movement of the-throttle valve the cani 38) leffects a follow-up acijustment of the motor ofv the transformer 33550 asto counterbalanee the signal voltage and effect aproportional position relationship between throttle valve and* waste gate.

The foregoingarrangement permits greater stabilityjof controlsine the waste gate is-actuated as a throttle valve position follow-tup, rather than as an intake manifold" pressure followrup as in the disclosure of application SeriaLNo'. 561,083.

llt' will'be readily seen that as the Waste gate isclosed the speed'of thek turbinewill 'be increased andthel superchargerrwill'T be driven by the turbine at an increasedKVV speed. An increase in the driving speed of the supercharger will 'effect-an increase in the pressure supplied tothe intake manifold whichjwill cause the bellows 26510 further contract moving the rotor winding 271%into a position A.Calling A for Vless pressure., andi effecting through; Windnasl and '.ZtlSot the. induction switch. .2.96, am; ratifier...Liendmntat 22.0A movement. of; ,the throttlein.: a .Closingg direction.. which. will mover. the winding-.291.; toward the null position. When the throttle valve-has reached this null point the combined voltages induced into the wind-ings 331 and 337 will neutralize stopping .the further opening of the wa; te gate 305.

Should the pressure within the intake manifold increase for any reason the bellows 265 will contract moving the rotor winding 271 in a direction calling for less pressure, whereupon the motor 220 will actua-te the throttle 3 in a closing direction and causing a difference in the combined voltages induced in the windings 202 and 204 through the winding 201, and the combined voltages induced in the winding 331 and 337 by the alternating current in the rotor winding 336.

This difference in voltage will affect the winding 321 of the motor 310 through the amplifier 350 in such a manner as to cause the motor 310 to rotate in a reverse direction tending to open the waste gate whereupon the turbine will be driven by the exhaust gas from the engine 4 at a slower rate effecting a decrease in the intake manifold pressure to the selected value.

From the foregoing it will be readily seen that there is provided novel means operable through power control lever 1 for first positioning the throttle valve in accordance with a selected intake manifold pressure, and further novel means for increasing this intake manifold pressure upon the throttle being positioned in excess of a null point including novel means whereby the speed of the supercharger may be regulated in accordance with the position of the throttle so as to maintain the pressure selected through operation of the power control lever 1. The selection of the intake manifold pressure may be varied as desired within the range of the system.

Overspeed responsive control circuit Stabilization of the waste gate actuator or supercharger speed control means motor 310 is specifically provided by a control system 400 including an alter nating current generator 401 driven by a shaft 402 from the supercharger turbine shaft 306 as shown and described in the copending application Serial No. 561,083.

Operation In operation, when the pilot through lever 1 moves rotor 77 according to a selected position, there is induced a certain combination of voltages in the stator windings 78, 79 and 80. These voltages are applied to the measuring follow-up transformers, for example, the follow-up transformer 259 in the manifold pressure control to thereby cause currents which produce a resultant field in its stator windings 260, 261 and 262.

If the position of rotor 271 of this follow-up transformer, determined by the manifold pressure acting on diaphragm 265, is such that the voltage induced in the follow-up rotor 271 is zero no control operation will be effected. If the rotor 271 is not in this position, as when the measured manifold pressure differs from the pilots selection, there will be induced a voltage in the follow-up rotor winding 271 the phase of which is determined by the direction of coupling.

The voltage from single phase rotor 271 is then applied through conductors 282 and 283 to stator Winding 207 of switch 206. This induces a corresponding voltage in rotor 208, which is carried by conductors 210 and 211 to the amplifier 215, the output of which amplifier feeds the secondary phase Winding 221 of the two-phase throttle actuator 220. The other phase winding 222 of this motor 220 is connected to the main source of alternating current.

The phasing between these voltages in the motor windings is such that the motor 220 actuates the throttle through gear trains 241 and 244, and in such a direction that the resulting change in pressure causes the diaphragm 265 to actuate transformer 271 toward the null position.

The same principle of operation applies to the governor actuator, which includes a follow-up transformer 93 positioned by a two-phase motor connected to the output of amplifier which operates as a direct followup from the pilots control lever 1 and the transmitter '76.

This transformer 93 is electrically connected to the pilots transmitter 76 in parallel with the manifold pressure transmitter 259, and if the position it measures differs from that selected, it feeds a signal to the input of amplifier 110 by conductors 100 and 101 from its single phase rotor 94. The output of amplifier 110 leads to the secondary winding 113 of the two-phase governor actuator motor 114 to adjust the pitch of the propeller of the aircraft through a suitable propeller pitch governor control. The pitch of the propeller being decreased as the selected manifold pressure is increased by movement of the control lever 1 in a clockwise direction.

In addition to the two-phase throttle actuator motor 220 there is provided the transformer 200 with rotor 201 and stator windings 202, 203 and 204. When the trans former 200 is used as a follow-up at small throttle lopenings, the voltage induced across the stator windings 202 and 203 thereof is compared with that induced across the stator windings 79 and 80 of the transmitter 76. The difference between these voltages is fed to stator winding 205 of induction switch 206, which through induction to rotor 208 is fed by conductors 211 and 210 to amplifier 215, and its output is fed by conductors 216 and 217 to the secondary winding 221 of the two-phase motor 220 to cause actuation thereof in the proper direction to position the throttle.

Whether the throttle actuator 220 is actuated as a direct follow-up from its connection with transmitter 76, or is actuated from connection with the pressure follow-up transformer 259 is determined automatically by cam 250 driven by the throttle actuator motor 220 through shaft 242, so as to control the position of the rotor 208 of inductance switch 206. The cam 250 is so shaped and so proportioned as to transfer from the direct follow-up connection with the transmitter 76 to a follow-up connection with the engine manifold pressure control follow-up transformer 259 at approximately 35 per cent open.

The transmitter 76 causes a direct follow-up adjustment of the throttle from zero to approximately thirty per cent open position and provides 4manually operable means for overcoming the effects which would otherwise be produced by controlling the throttle valve through the intake manifold pressure in view of the characteristic inversion of pressure at the intake manifold of an engine which occurs upon adjustment of the throttle valve to somewhat less than thirty per cent open. Moreover the latter manually operable means facilitates the starting of the engine.

Thus when moving the pilots control lever 1 in the range corresponding to the zero to thirty per cent throttle valve open position, proportional opening of the throttle valve is accomplished and the throttle valve follows the position of the control lever 1.

When the throttle valve is in a position above thirtyfive per cent open, the throttle valve is in pressure follow-up, that is, the same is positioned in accordance with the intake manifold pressure selected by the pilots control lever 1.

When the throttle valve is between thirty per cent and thirty-five per cent open the signal to the amplifier 215 is a combination of position follow-up and pressure follow-up. The reason for the latter arrangement is to provide a smooth transition from the position followup to the pressure follow-up.

With reference to the throttle actuator motor 220 the rotor winding 201 of the rotary transformer 200 is arranged to induce a voltage in the stator windings 202 and 204 which are in turn connected to the stator windings 331 and 337 of the transformer 335.A The rotor duce an opposing voltage `in#A the vlatter vstator -windingsI 3311 and4337.vv The-differencebetween-thef saidopposing'rvoltages determines the direction of rotation-of 'the' motor 310. The said rotor windings 201 and 336 being sowarrangedfthat when the throttlevalveis* positioned below apredetermined null- Lpoint of -say\ aboutsixty perl centopen the Ymotor -310-wi11 be Vactuateddaar-direction` for opening -thewaste gate 30S-so as to--decrease--the speed of the superchargenY Conversely; when thethrottle valve is inapositionmore than the said/null position orl aboutl sixty per cent'open themotor-310-willbe driven ina direction for closing the wastegate -so as to increase thedrivng speed ofthe auxiliarysupercharger and -therebyithe; pressure within the intake manifold; Such-` operation Y position, the, throttle transformer 200 causes asignal voltage to be transmitted to the amplifier ,350,` which in turn operates,k the two-phase waste-gate motor 310, to close the waste gate as a position -follow-upof thethrottle rate and increase the turbine speedas' previously explained. This will cause an increase .in supercharger output, and thereforean increase in manifold pressure.

Should the pilot now select a different pressure by. moving the transmitter rotor 76, the measured manifold v1 pressure and selected pressure will differ, and the throttle will then be moved to produce the desired` value. Since the throttle actuator transformer 200 'has moved ,from thebalanced position, it causes a signal to be transmitted to thewaste gate actuator1 follow-up motor 310 tochange its setting and follow the positionof the throttle valve.

If the. selected pressure is such that the throttle is held ina position less than the null position ofsxty percent open., the system. will hold the waste gatewide open.

On the other hand, if a high pressureis selected,' so that the turbine is operating at top speed'aslirnited bythe overspeed controlnetworlg 400, the throttle will be Open e d more than the nullposition to produce the selected Apres- Slllf,

Further.. iu .order ,to addtabilitv to. the..Systomnarate Circuit isnrovidod. in the circuit. 400 for .preventing ao- Celeration or deceleration. of. thosuporchargcr in exoess-of i a. Controlled, limit, as disclosed in .the .conceding applica-.Yk

power is on, the electromagnetic.clutch is connectedto V the, automatic throttle actuator means.L If the` power is turned'pi, the clutch 2 shifts the connection ofthe throttler fromlhe automatic throttle actuator.y means tov ,a mechanical connection for manuali operation by leven` 1 through clutch 2. When the power is turned. ,oi a ,sui t able `spri ng,.m ay heprovided which will openthe, ,waste sate, f and the` Propeller: pitch governor. .will remain atthe.l setting. in which it happened .to. be` at .the..t1rme. thatgthe power wasturned oi M ulti-engineA :control-` There is provided in the present invention a-k novelsinglelever -control for multi-engine operation; Inethe application-Serial No.4 561,083 filed October30;-l944=by" Joel D'.. Peterson,- separate controlAA levers-i-wer e proyidedy for the control system? of'geacl-r engine.MA

a novel? single levercontrolfor-- the Vcontrol systems;r of?l twoormorel engines supplying balanced power,` toA an aircraft and further-- provides :novel-means forA selec-'- tivelyY varying the ypower appliedat one-\sideor the other ofthe aircraft by-such engines.

Duringttake-oif; theI natural tendencys'is for a-balancedpower multi-engine aircraft to-veeror turn-fromfadiied course Adue-to engine torque or the direction of rotationof-thepropell'er blades. In order-to steerthee-airplane atined direction under such conditions, the-engine powerntirone side of the plane may-be -reduced so as tofbalance-A the tendency of the plane vtoveer.r This-expedientHmay-- also be used toy overcomerthe tendency: of fcrosswinds to changeA the direction, of th'ecraft.

Referring to the drawing of Figu`re1-2,there-is illustrated' di'agrarnrnatically` the-.subject single-lever controljfor'amulti-engine aircraft. Thecontrol includes -a-shaf-t v'S50-J Lo `which may beimpartedrotary motionftoy operateftlie master transmitter' 76'Which-rnay-v inc1ude=a standardl rotorwinding 77 'inductively' coupled to-separatestator windings-73, 791and280-for each engine'controlsystem:A As an alternate-meansY separateitransmitters forweachengine control system may be provided 'inwhiclthe" rotors 77 of the'respective transmitters are mechanically' connected for rotation by the single controlyshafPSS- oras a further alternate arrangement a single master trans;-v mitterrnay'beprovided with the severalyreceiver systems shown in Figure l connected inv parallel thereto.l Asshown in Figure 2 thel respective-statorwindngsf78, 79 `and S0 are sofarranged thatmaximumcoupling between` therotor 7'! Aand each`r stator winding occurs atthe sameangular position of the rotor 77. Thus during normalVJ operation, the. respective engines controlled by the system provide balanced power to the aircraft at opposite sides v thereof.

There is further provided; inthe line'Z'll of-eachof-` the --engine control systems a-winding552'to which there may be-inductively. coupled Va 'winding-554connected" across -lines 631and 64 of themainsourceof-alternatingw current. The windings 554V are normallypositioned'fat`v right angles to the windings 552,. as indicated in Figure 3, and out of inductive relation with the winding 552.

Howeverr upon; axialV movement ofytheacontrolzishaft 55.01; fromV the balancedy positon, shown in; Figure..3, t one on the other of the-windings 554 wi1lbe actuatedfthroughzaa lever 556-pivoted at558fand bearingat onefendruponf a `collar 560 ,-formedon.- the shaft 55.0., Anspringz; 5621: biases; the :lever: 556.l into contact-ing; relation with.: their collart), while,.agstopg5 64 limits.V the movement of-ztheylever S56-toward the .collar 560.`

Theoppositefendof the lever 556 isz-linked@ an: arm S68A whereby: rotary n1ovement.-may:betirnparted mother; rotarywindingl 554.

It will berseen from; the, foregoing thantheregispro .videdia mechanical arrangementwhereby the rotoruwindsA ingsg554 may alternately he rotated. throughxannangle-.a The windings 554 are, sox set-that1 null ole-.zero .couplingrx exists; between rotor winding 554 and vstator :wi-ndingxSSZl; in the normal balanced positionl shown;-A Moreoverguponz. axial movement .ofV the shaft 5501-fromf-the 'nulluposition rotation :ofk one;- of the :windings 554 is. eieotedzA into :cou-v pling. relation with .thewindingv552. 'lhefpalternatng-z-- voltage inducedfintol the. windingt 552is i of suena phase;- as -to cause,l upon A amplification. rotationl ofzzthei actuator motor1220in athrottle valve closing directionfandethereat byf decreaseV =the` -intake manifold. pressure setting lofi-the 'y engine attone-.fsideoftheaircraftwithout effecting thein'a. take manifold pressure setting;ofnthe-enginerat StheifopN posite.- side. of :the f aircraft since. the.- other :;lever..;-55 6s heldfrom rotation .-by its stop .564.. However axial movement :of zthe shaftf 5502 in` an opposite direction; from theH nullposition will similarlyi .move theotlier:rotore-wind ingf554'from its null positionsoastta-decrease tliqfintakt manifold pressure settingv of the engine at theeotlier side'` -of the aircraftg witheuteiecting -the-nullposition-of-ithe first mentioned rotor winding S54, Thus there is provided a novel intermittent drive whereby the intake manifold pressure in the engine rxr engines at one side of an aircraft may be reduced without effecting an increase in the intake manifold pressure setting of the engine or engines at the opposite side of the aircraft.

The stops 564 may be eliminated so that the intake manifold pressure of the engine or engines at one side of the aircraft is reduced while the intake manifold pressure of the engine or engines at the other side of the aircraft is increased upon axial movement of control shaft 550 to one side of the null position and thereby effecting unbalanced power to control the direction of the aircraft.

In the event there are provided more than one engine at opposite sides of the aircraft, each of the rotor windings 554 may be inductively coupled to stator windings corresponding to windings 552 in the control systems of the respective engines at one side of the aircraft so as to permit the power applied by the multi-engines to be unbalanced in like manner at the will of the operator through manipulation of the single power control shaft 550.

AS a further alternate form of the invention, the main control lever, as shown in Figure 3, may be of the type shown in Figure l and indicated by the numeral 1 with the addition of a manually operable ball 570 mounted on the lever 1 and driving through a shaft 572 a pinion 574 engaging a rack 576 to impart axial movement to shaft 550 as described with reference to Figure 3. The lever 1 may be rotated with a shaft 580 in a suitable bearing. The shaft 580 is arranged concentric with the shaft 550 and -there is slidably mounted in shaft 580 the rack 576. Thus the lever 1 may be manually operated to position through rod 70, the rotor 77 of the transmitter 76 for the respective engine control systems.

It will be seen from the foregoing that any one or all of the foregoing improvements of Figures 1 3 may be applied to the basic system which has been heretofore described and claimed in the copending application Serial No. 561,083, filed October 30, 1944 by `loel D. Peterson.

Although only three embodiments of the invention have been illustrated and described, various changes in the form and relative arrangements of the parts may be made to suit requirements.

What is claimed is:

l. For use with an aircraft having engines mounted at opposite sides thereof to normally supply a balance of power, and each of said engines having a throttle valve to control the intake manifold pressure therefor; the combination comprising an actuator motor for each engine throttle, an intake manifold pressure responsive control for each actuator motor to maintain the intake manifold pressure of its associated engine at a preselected value, a single manually operable member, first means cooperating with said member to select said pressure value upon adjustment of said member in one sense, and second means cooperating with said member to vary the selected pressure for said engines upon adjustment of said member in a second sense.

2. The combination defined by claim 1 in which said manually operable member includes means to select the intake manifold pressure for the engine at one side of said aircraft independently of the selected intake manifold pressure for the engine at the opposite side of said aircraft.

3. For use with an aircraft having engines mounted at opposite sides thereof to normally supply a balance of power, and each of said engines having a throttle valve to control the intake manifold pressure therefor; the combination comprising an actuator motor for each engine throttle, an intake manifold pressure responsive control for each actuator motor to maintain the intake manifold pressure of its associated engine at a preselected value, a single manually operable member, a first means cooperating with said member to select said pressure value upon rotation of said member, and second means cooperating with said member to vary the selected pressure for said engines upon axial movement of said member.

4. The combination defined by claim 3 in which said second means includes an intermittent drive for effecting upon axial movement of said member in one direction a reduction in the selected pressure for the engine at one side of the aircraft only.

5. The combination defined by claim 3 in which said second means includes an intermittent drive for effecting upon axial movement of said member in one direction a reduction in the selected pressure for the engine at one side of the aircraft only, a second intermittent drive for affecting upon axial movement of said member in an opposite direction a reduction in the selected pressure for the engine at the opposite side of the aircraft only, and stop means for limiting the action of said first and second intermittent drives in response to the axial movement ot said member.

6. For use with an aircraft having engines mounted at opposite sides thereof to normally supply a balance of power, and each of said engines having a throttle valve to control the intake manifold pressure therefor; the combination comprising an actuator motor for each engine throttle, an intake manifold pressure responsive control for each actuator motor to maintain the intake manifold pressure of its associated engine at ya preselected value, a manually operable member, means cooperating with said member to select said pressure upon rotation of said member, an axially movable device carried by said member, means cooperating with the axially movable device to vary the selected pressure for the engines at opposite sides of the aircraft upon axial movement of said device.

7. For use with an aircraft having engines mounted at at opposite sides thereof to normally supply a balance of power, and each of said engines having a throttle valve to control the intake manifold pressure therefor; the combination comprising an actuator motor for each engine throttle, an intake manifold pressure responsive control for each actuator motor to maintain the intake manifold pressure of its associated engine at a preselected value, a manually operable member including means to select said pressure upon rotation of said member, and other manually operable means carried by said member to vary the selected pressure for the engines at opposite sides of the aircraft.

8. The combination defined by claim 7 in which said other manually operable means includes a manually rotatable member, a rack cooperating with said rotatable member and axially movable, means including an intermittent drive cooperating with said axially movable rack to effect a reduction in the selected pressure for an engine at one side of the aircraft upon axial movement of the rack in one direction, and stop means limiting movement of the drive upon axial movement of the rack in an opposite direction.

9. For use with an aircraft having engines mounted at opposite sides thereof to normally supply a balance of power, each of said engines having a throttle valve to control the intake manifold pressure therefor, a supercharger for said intake manifold, and a speed control for the supercharger; the combination comprising an actuator motor for each engine throttle, a first position measuring device controlled by said actuator motor, an actuator motor for each supercharger speed control, a second position measuring device controlled by said speed control actuator, means operatively connecting the first and second position measuring device of each associated engine so that the position of the speed control actuator is directly proportional to the position of the throtle control actuator, an intake manifold pressure responsive control for each throttle actuator motor to maintain the intake manifold pressure of its associated engine at a preselected value, a manually operable master control member including means to select said pressure by rotation of-'E said" member; and" other' manually operable meansJ carried -lay-'said'-memberto var-yjthe 1selected'rpressure for 1 the engines at opposite'sides of the 'aircraft'.l

l0. The combination delinedby claim 9`in which said other manually operable=meansincludes a manually rotatable-memb'en a rack cooperating with ysaid"rotatable'vk member and axia1ly=movable, means includingan intermittent drive cooperating with said'axially movable rack to effect a reduction in the kselected pressure` for an engine -at one-side oftheaircrait upon `axial movement" of the rack in one direction, andra` second stop means limiting movement ofi the drive-upon-axial'movement ofthe rack in an oppositefdi'rectionA 11.- For use-with an aircraft=havingfengines'mounted' at opposite sides-"thereof to normally'supplywa balance of `power,v andy each of fsaidiengines having an' intake condnitand a throttle''valvefforcontrolling flowv of combustible'fmixturesto--its associated intake conduit; thecombination comprisingautomatic means for 'each` of said' engines responsive-to engine intake pressure for-position ing itsassociated*valve,` inductive coupling'means -for adjusting'th'eA datum'of saidiautomatic means, a manually operable member, means operatively connectingsaidl manually operable member -tof said inductive coupling` means for varyingth'e'datnm' of--the automatic means' for both' of vsaidf'enginesproportionately upon movement of-saidl manually-'operableamember in onesense, and other means operatively-Y connecting sald manually operable member `to said: inductivefcoupling means for varying the/1 datum-of the automatic'meansfor--each of'said'engines disproportionately# upon actuation' offsaid manually' op-Y erable member in= another sense:

l2. Arnultienginecontrol` comprising in combination control means for selecting-an operating condition of each of "said engines'in' unison; independently operable othery control means for varying'saidfoperating conditionfof'atleast-"one'of saidengines'-relativeeto the other ofsaid engines, and a manually'operable member including rst|- meansfor operating the ist mentioned of said controlv means upon rotationl of "said 'member and second 4means for operating the oth'enofesaidfcontrol means upon axial movement of said memberztofselect'the operating .condition. of said oneengine-.independentlyof said selectedop erating condition. offlthes other fof: said engines.

13.. AJmulti-engine:control .comprising inl combination f control means for selecting an operating condition-ofv eachrof said .'enginesriin unisom independently l.operable other controly means..for varyingrfsaid operating-condition of at least oneof: said enginesnelative to the other of saidengines, a manually' operablememberg. afrotatable shaft operably-connecting rsaidfmemberrrtothe 'rst mentioned of said .control meansfruponvrotation ofsaidmember, aw collar affixed) to said: shaft?,` and; linkage means operatively connectingrsaid-collar tofsaidffothercontrol means upon axial movement offsaid member to: select the r operating condition of said one engine independently of said selected! operating-.condition ofthe other'of said engines.

14. A multi-engine control"comprising a'separate -reg-` ulator. for each of -the.controlledfengines a rstinduction transformer means Ihaving la rotatable winding means 16 adnstablypositioned forV changing the' datumoff'each-- of "said-regulators; arsecond inductionl transformer means Having la-rotatable winding meansadjustably*positionedl for independently varying the datum'of Vatleast oneo'f.s said 'regnlatorsrelative to the datum ofthe-other of` said regulators, a third induction transformer means havingga rotatable" winding 'means adjustably positioned 1for independntly'varying-the -datum of said otherregulator'rela-A tive-tov the"datum-of'said oneregulator, a movablev ele." ment, a pair'of 4collars laliixed'to said element, rst "linkage` means'for operatively connecting one of said collars'rto" therotatable' windingmeans of saidsecond induction' transformermeans upon axial'movement'of said ele* ment/in one sense,I Second linkage' meansfor Voperatively connecting-the other-of said'collars `to the vrotatable vvind=C ing means Aof* said third inductionr transformer meansm upon-laxial movement'of said'element in an opposite." sense; andmanuaily operable means foradjusti'ngjtlz'ten rotatable winding-fmeans of' said' first inductionl trans= vformer Ameans and for `axially adjusting; said element to winding means of fsaid first induction transformermeans,"

and" a` manually; operable -member loperatively connected-' to said:1 elementfor imparting rotaryf'movementto'saidi element for adjusting the rotatable `Winding 'means 'o'said' i first tindnctionftransformerA means and axial movement" -to said element toselectivelymontrol' the rotatable wnd-t ing :means of "said second` andl third induction transformer means;

16;'Tl'1`e combination defined' by" claim-14 including a manually operableleveroperatively connected tother rotatable Windingfmeansof saidv first induction'ftransf former means; and-a manually rotatable element carried by* said-l lever and'operatively connected :tof said'fele'ment" for imparting axialfmovementl thereto for'selective1ygcon trolling the Lrotatable Winding' means of'saidsccondffandA third*inductionwtransformer means.r

References-:Cted lin the lile olf-.this` patent UNITED STATES' PATENTS Ridgiey .et a1 .Juiy. `12.11.1945: 

